The subject matter disclosed herein relates generally to rotary wing aircraft and, more particularly, to a dual rotor, rotary wing aircraft.
A typical rotary wing aircraft, or helicopter, includes a main rotor assembly that provides lift for the aircraft. The main rotor assembly is secured to an airframe that often includes an extending tail. In many such aircraft, a tail rotor or auxiliary propulsor is located at the extending tail. Some main rotor assemblies are configured as dual coaxial rotor systems, having an upper rotor assembly rotating in a first direction and a lower rotor assembly, coaxial to the upper rotor assembly and rotating in a second direction opposite the first direction. Further, some dual coaxial main rotor assemblies are configured as a rigid rotor system, removing certain degrees of freedom of the upper and lower rotor assemblies to allow for decreasing spacing between the upper and lower rotor assemblies and increasing high performance capabilities of the aircraft. The use of a dual coaxial, rigid rotor system, however, tends to produce significant vibration in the airframe and aircraft systems during operation.